Manufacture of naphthalene



Patented Aug. 20, 1940 UNITED STATES:

2,212,018 MANUFACTURE onNArn'rnALnNE Aristid V. Grosse and WilliamJ. Mattox, cago, Ill., assignors to Universal Oil Product.

Company, Chicago,

ware

111., a corporation of Dela- No Drawing. Application June 28, 1937, Serial No. 150,760

3 Claims. (01. 2601-668) This invention relates more particularly to the ble mechanisms involving the existence manufacture of naphthalene by reactions involving dehydrogenation and cyclization of aliphatic hydrocarbons.

In a more specific sense it is concerned with the application of the'foregoing types of reactions to aliphatic hydrocarbons of a definite configuration having 10 carbon atoms in straight tems. The present process provides for the manufacture of this valuable compound by a specific process in which naphthalene formation is the principal reaction and in which high yields of relatively pure naphthalene are produced. The decanes or similar charging stocks submitted to the reactions of the process may be produced by any convenient method such as, for example, by the fractionation of a paraifinic gasoline to produce a cut-containing relatively;"'high percentages of n-decanes. j In one specific embodiment the present iry'vention comprises the production of naphthalene by subjecting n-decane to temperatures of the order of 50 0650"C. for a period of time of from approximately 0.1-15 seconds under-atmospheric pressure while in contact with catalysts comprising active aluminum oxide supporting minor percentages of chromium sesquioxide.

In further embodiments, n-decenes or the al kylated derivatives of aliphatic hydrocarbons containing '10 carbon atoms in straight chain arrangement may be substituted for n-decane and alkyl derivatives of naphthalene also produced. In these alternative operations the temperature and time of contact with the catalysts may be varied to accommodate the varying molecular weights and structures of the charging materials.

The reactions involved in the present process are typified 'by the following structural equation:

Naphthalene, 010B.

of intermediate products since several possibilities exist although they are hard to check by well-defined analytical procedure. For example, it is possible that partial dehydrogenation of the decanemc- 5 ours with the primary formation of a single ring with alkyl substitution sincev separate experiments have indicated that naphthalene is also productible by the dehydrogenating treatment of butyl benzols, which may therefore existas intermediate products. Furthermore, the above equation does not take into account the known facts that there are a considerable number of side reactions which result in the formation of both-aliphatic and cyclic hydrocarbons of both higher and lower molecular weight than naphthalene. Again if instead of n-decane or n-decenes, alkyLsubstituted homologs are employed,

there is some production of alkyl derivatives of naphthalene. However, there is at all times a substantial and worthwhile production of the desired main product so that the process is of a practical and commercial character.

Kccording to the present invention, the preferred catalysts for selectively dehydrogenating and cyclingdecanes to produce naphthalene have been evolved as the result of a large amount of investigation with catalysts having a general dehydrogenating action upon various types of hy-- drocarbons such as, for example, those which are encountered in the fractions produced in'the distillation and/or pyrolysis of petroleum and other naturally occurring hydrocarbon oil mixtures. Catalysts whose preparation and proper;

ties will be presently described are particularly empirical basis; though at times certain groups v of elements or compounds have been found to be more or less equivalent in accelerating certain types of reactions. For example, the noble metals, platinum and palladium, have been foundto be effective in dehydrogenating reactions, particularly in dehydrogenating naphthenes to form aromatics, but these metals are expensive and easily poisoned by traces of sulfur so that their use is considerably limited in petroleum hydrocarbon reactions. 56

The preferred catalysts consist of activated aluminum oxide (preferably slightly alkalized) supporting less than 15% and preferably about of chromium sesquioxide. It is essential to the preparation of these active and selective catalysts for dehydrocyclization reactions that this aluminum oxide possess certain structural characteristics permitting the maintenance of a stable deposit of chromium sesquioxide on its surface which is essentially undisturbed under the conditions of operation and when regenerating by burning ofi carbonaceous deposits with air or other oxygen-containing gas mixtures. Aluminum oxide which is generally preferable as a base material for the manufacture of catalysts for the process may be obtained" from some natural aluminum oxide minerals or ores such as bauxite or carbonates such as Dawsonite by Al2O3.2H2O and diaspore having the formula A1zO3.H20. Of these two minerals only the corresponding oxide from the bauxite is suitable for the manufacture of the present type of catalysts and this material in some instances has given the best results of any of the base compounds-whose use is at present contemplated. The mineral Dawsonite having the formula NazAl (CO3) 3.2Al (OH) 3 is another mineral which may be used as a source of aluminum oxide, the calcination of this mineral giving an alkalized aluminum oxide which is apparently more effective as a support in that the catalyst is more readily regenerated after a period of service. Alumina in the form of powdered corundum is not suitable as a base.

It is best practice in the final steps of preparing aluminum oxide as a base-catalyst to ignite it for some time at temperatures within the approximate range of from GOO-750 C. This does not correspond to complete dehydration of the oxide but gives a catalytic material of good strength and porosity so that it is able to resist for a long period of time the deteriorating effects of the service and regeneration periods to which it is subjected.

Our experiments have further disclosed that in the presence of the preferred selective catalysts whose preparation has just been described, there is a relatively narrow range of conditions which are optimum for producingcommercial yields of should be considerably shorter, of the order of from 0.1 to 2.0 seconds. Under these conditions there is about a 25% yield of naphthalene based on the weight of the n-decane charged. There is also a production of considerable yields of butyl benzols and methyl-propyl benzols to an extent of 50-75% of the n-decane charged. By a proper fractionation and segregation of the products,.

therefore, recycle material is available so that in this type of operation the ultimate yield of naphthalene may be as high as 50%.

The following example is introduced to indicate the yields and character of the product produced by the application of the present process although not with the intent of unduly limit its scope.

n-decane was vaporized at atmospheric pressure and passed over a granular catalyst comprising approximately 96% activated. aluminum 'oxide and 4% chromium sesquioxide at a temperature of approximately 500 C. (932 F.) and a rate of flow was employed which permitted a time of contact of 15 seconds. In a single pass a 25% yield by weight of naphthalene was produced, the product melting at 80.1 C. By recycling of unconverted decane and a fraction comprising a mixture of butyl, benzols, the ultimate yield of the desired naphthalene was brought to 50% by weight of the n-decane charged.

The foregoing specification and example have sufllciently described and illustrated the character of the present ,invention and the results obtainable thereby although neithersection is intended to-ig unduly limiting.

We*claim as our invention:

1. A process for the production of naphthalene from aliphatic hydrocarbonahaving 10 carbon atoms in straight-chain arrangement, which comprisesdehydrogen'atingand cyclicizing the aliphatic hydrocarbon by subjection to a temperature of the order of 500 to 650 C. for a period of about 0.1 to 15 seconds, in the presence of catalytically active aluminum oxide containing a relatively small amount of chromium sesquioxide.

2. The process as defined in claim 1 further characterized in that said aliphatic hydrocarbon comprises n-decane.

3. The process as defined in claim 1 further" characterized in that said aliphatic hydrocarbon comprises n-decene. I

ARIS'I'ID V. GROSSE. Will-1AM J. MA'ITOX. 

